Yeh I agree, putting a more believable light source on this would definately help this piece along, at the minute im afraid to say it has a strong pillowshaded look about it in places, as if parts of the body are lit from the center outwards, try maybe shading this as if the lights hitting from somewhere above. For consistancy of form its definately a good idea to flip parts of the body for a guide of sorts so that like an arm isn't noticably larger or smaller in comparisant to the other but think of giving each arm unique attention and definately shade them appropriately, plus variation with their positioning could make it look more natural.
I think you could get some stance inspiration from actual apes, I know they're they saiyens transformed but in this form they are technically just huge enraged apes. There's more you could do with the posture to express this, they're like bulls seeing red. Mind you im not sure what this is going to be used for. This might be of some inspiration, Kong (first thing i thought of probably not a great example), im not saying do it like this but im sure it's better to have some ape references to push you in the right direction to give it more interest there's bound to be some great images out there to help, even from the cartoon getting the style down n all.
http://www.adriandale.co.uk/wp-images/KingKong.jpghttp://www.youtube.com/watch?v=3nO-vNLOSxk